Method of and photonic device for eliminating or substantially reducing sensitivity to polarization of an injected optical signal and method of manufacturing such photonic device

Abstract

An photonic device, comprising one section of a material which is different from the material of another section such that the two sections present different optical birefringent index values. This causes a first set of polarization modes to move in a spectral space with a different velocity than a second set of polarization modes. A bias current, or voltage, is used for controlling the overall birefringence effect in the device. The biasing for controlling the birefringence effect is performed such the TE modes and the TM modes of the device are made to coincide in their respective spectral position. Thus the device is made insensitive, or presents substantially reduced sensitivity, to the polarization of any incoming optical signal.

The invention claimed is: 
     
       1. An injection-locked photonic interferometer, comprising:
 a first section including an optimized polarization-insensitive gain material; and 
 a second section including a birefringence optimized passive material, the first section having a different optical birefringent index value than the second section, and in response to an injected optical signal the first section and the second section are configured to cause a first set of polarization modes associated with the first section to move in a spectral space with a different velocity than a second set of polarization modes associated with the second section. 
 
     
     
       2. The photonic interferometer of  claim 1 , wherein the photonic interferometer comprises a laser diode or an optical filter. 
     
     
       3. The laser diode of  claim 2  wherein in response to the injected optical signal a total birefringence generated in a laser cavity is reduced to null, or is reduced. 
     
     
       4. The laser diode of  claim 3 , wherein an active section is made of bulk tensile strained material. 
     
     
       5. The laser diode of  claim 3 , wherein the structure of the polarization-insensitive gain material includes,
 a buffer layer of InP material, 
 a first optical confinement layer of strained InGaAsP material, 
 an active gain layer of strained InGaAsP material, and 
 a second optical confinement layer of strained InGaAsP and a top layer of InP. 
 
     
     
       6. The laser diode of  claim 5 , wherein the first optical confinement layer is of a thickness of about 200 nm; the active gain layer is of a thickness of about 120 nm; the second optical confinement layer is of a thickness of about 200 nm; and the top layer is of a thickness of about 200 nm. 
     
     
       7. The laser diode of  claim 2 , wherein the birefringence optimized passive material is made of a compressively strained bulk structure. 
     
     
       8. The laser diode of  claim 7 , wherein the birefringence optimized passive material is a stacked structure with an adjusting layer of InP:Be;
 a strained bulk layer of InGaAsP; and 
 a top layer of InP:Si. 
 
     
     
       9. The laser diode of  claim 8 , wherein the strained bulk layer of InGaAsP has a thickness of about 420 nm and the top layer of InP:Si has a thickness of about 250 nm. 
     
     
       10. The laser diode of  claim 2  comprising:
 a modulation section having a volume configured to reduce or minimize carrier variation during modulation. 
 
     
     
       11. The laser diode of  claim 2  comprising:
 an active material with a reduced or minimized phase-amplitude factor configured to introduce a reduced or a minimal index variation during amplitude modulation. 
 
     
     
       12. The laser diode of  claim 2  comprising:
 an off-cavity saturable absorber configured to enhance a dynamic extinction ratio of a modulated signal. 
 
     
     
       13. An optical network unit for use in fiber to the home access networks, comprising the device of  claim 1 .